Muscle-powered watercraft

ABSTRACT

A muscle-powered watercraft includes flotation and propulsion structure having at least two blades which remain rigid under the stresses that are subjected to. The front edges of the blades are hinged about respective axes transverse to the watercraft&#39;s axis of propulsion, spaced from one another along the axis of propulsion on either side of the watercraft&#39;s center of gravity. Each of these blades extends symmetrically from the axis of propulsion. Abutment structure limits the angle of freedom of each blade about its hinging axis, and the volume of water displaceable by immersion of the flotation structure is selected to correspond to 1 to 2 times the total laden weight of the watercraft. The flotation structure has feet-supporting surfaces distributed about the craft&#39;s center of gravity, whereby a driver may impart to the watercraft a sinusoidal movement in and out of the water by pitching the craft and hence making the blades operate in opposition to one another between the abutments.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates to a muscle-powered watercraft comprisingflotation means and propulsion means having at least two blades. Theseblades may be made of a single part or in certain cases of two partsjoined rigidly together by a common axle so that they can be consideredas constituting a single blade having two parts.

Many watercraft of this type are known, at least from the literature.However none of them can be considered as a commercial success becausethe energy efficiency is low and the movement to be performed makes hardwork, so the public instead prefers more conventional watercraft such asrowing boats or pedalos.

The research leading to the present invention has been directed to threepoints: firstly a play-like, sporting, balancing movement which candevelop a feeling for water; secondly a substantial improvement of theenergy efficiency; and lastly an original mode of operation whichconsists in causing the watercraft to plunge in and then out of thewater with a constantly-propulsive sinusoidal trajectory.

To this end, the invention concerns a muscle-powered watercraftcomprising flotation and propulsion means having at least two bladeswhich remain rigid under the stresses they are subjected to,characterized in that the front edges of the blades are hinged aboutrespective axes transverse to the watercraft's axis of propulsion,spaced from one another along said axis of propulsion on either side ofthe watercraft's center of gravity, each of these blades extendingsymmetrically from said axis of propulsion, there being abutment meansfor limiting the angle of freedom of each blade about its hinging axis,and the volume of water displaceable by immersion of said flotationmeans being selected to correspond to 1 to 2 times, preferably 1.2 to1.5 times, the total laden weight of the watercraft, said flotationmeans having feet-supporting surfaces arranged about the craft's centerof gravity, whereby a driver may impart to the watercraft a sinusoidalmovement in and out of the water by pitching the craft and hence makethe blades operate in opposition to one another between said abutments.

The advantage of this watercraft comes from two elements which incombination enable a substantial improvement of the propulsion energy.One of these elements is the use of rigid blades freely hinged betweentwo abutments, which is a simple and efficient system. The other is theuse of flotation means which, in response to a pitching movementcommunicated to the watercraft, allow the watercraft to adopt asinusoidal movement in and out of the water. Due to this movement, thetwo blades situated on either side of the watercraft's center of gravityoperate in phase opposition but produce forces directed alternatelyupwards or downwards and each having a component in the direction ofpropulsion. The sine may have a substantial amplitude so that the idlemovements during which the phase inversion of these blades tipping fromone abutment to the other represents only a small proportion of thetotal propulsive movement. In any event, this tipping phase of theblades does not constitute a loss of efficiency because at that momentthe downwardly- or upwardly-acting vertical force is in a no-loadsituation; only a small fraction of the force is needed to produce thetipping itself. As there is no resistance, the speed of the movementincreases and when it reaches the abutment at greater speed, the forceis restituted. Moreover, each user may adjust the degree of flotabilityof his watercraft as a function of his own weight and muscular force,which enables the production of sinusoidal movements in and out of thewater of greater or smaller amplitude.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings show, schematically and by way of example,three embodiments of the watercraft according to the invention.

FIG. 1 is a plan view of a first embodiment.

FIG. 2 is a view in longitudinal cross-section along line AA' of FIG. 1.

FIG. 3 is an elevational view of the watercraft carrying a driver.

FIGS. 4a to 4d are side elevational views of this watercraft showingfour phases of the sinusoidal movement in the water.

FIG. 5 is a plan view of a second embodiment.

FIG. 6 is a cross-sectional view along line V-V' of FIG. 5.

FIGS. 7a and 7b are elevational views of the watercraft carrying adriver, in the two pressure-applying phases.

FIGS. 8a to 8d are four elevational views of the watercraft of FIG. 5showing different phases of the sinusoidal movement.

FIG. 9 shows a third embodiment.

FIG. 10 is a cross-sectional view along line VI--VI of FIG. 9.

FIGS. 11a to 11d are four elevational views of the watercraft of FIG. 9showing different phases of the sinusoidal movement.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1 and 2 illustrate a watercraft comprising a central float 1 towhich are pivotally mounted two blades 2 and 3 by their respective frontedges. These blades extend transversally and are situated respectivelyin front of and behind the watercraft's center of gravity. In FIG. 2,the pivoting axes of the forward and rear blades are shown situated onthe central longitudinal axis of the float, but these axes could be offsuch alignment, in particular they can be lowered so that these bladesremain submerged during operation to avoid "cavitation" phenomena.

The float encloses a free space 4 accessible by means of an obturator 5which allows adjustment of the watercraft's degree of flotability byusing a suitable ballast such as water.

The ballast is preferably formed of a liquid phase 26, a dividedparticulate solid phase preferably in the form of pellets 28, or amixture of the two. This enables two functions to be achieved. Onefunction is to adjust the watercraft's flotability. The other, by meansof the mobility of the ballast accompanying the watercraft's oscillatingmovement, is to amplify this movement hence reduce the muscular effortor increase its output by free movement of the ballast in the free space4, under its inertia. Of course, the shape and volume of the space 4 canbe selected with a view to amplifying the ballast's inertia effect.Thus, this shape and volume can be designed to create zones able tocontrol the flow of liquid or pellets or their mixture inside the volumeto maximize conversion of the inertia effect into a propulsive movementof the watercraft. The mass of the ballast can be adjusted as a functionof the desired performance of the watercraft. Ballast can be added witha view to covering long distances at reduced muscular effort. Ballastcan be removed to make the watercraft easier to control.

The blades have a density about the same as water so that when submergedthey neither rise nor sink on their own. The front blade 2 has a cut-out7 whose front end 7a serves as pivoting axis and engages in a groove 6provided at the front end of the float and whose rear end 7b can beformed by a rod fitting in an arcuate opening 8. Two abutments 9a and 9bformed for example by adjustable screws limit the angle of pivoting ofthe blade 2. Any other arrangement for the same purpose may beenvisaged, notably dispensing with the arm 7b and the opening 8. In sucha case, the abutments could be formed by lateral projections provided onthe float. The groove 6 can be a hole.

The rear blade 3 is pivotally mounted between two adjustable abutments10a and 10b fixed on the central float 1.

As regards the blades, we have tested other possibilities than thatdescribed above. Such possibilities include the use of materials ofcontrolled elasticity which can be advantageous notably as regards lessabrupt navigation of the watercraft, but the energy output is not sogood because any elastic system consumes part of the energy it receives.

Spring-loaded blades: for these blades, which are rigid and pivoted aspreviously, the abutments are replaced by biasing return springs orelastic blocks, wound around the pivoting axis or directly connectingthe blades to the float. Such blades are horizontal at rest and pivotunder the action of vertical forces Ff and Fr, compressing the springsand adopting approximately the same propulsive positions that theypreviously had against the abutments. During the next phase, the springsrestitute a part of the stored force.

Semi-rigid elastic blades: these blades deform elastically in responseto transverse pressure and their flexibility increases from front torear. These blades can be of a composite reinforcing fiber/polymericmaterial having fiber layers decreasing from the front to the rear, butmay also be made of any elastic material having a tapered profile and anappropriate modulus of elasticity.

Such blades can be pivoted between two abutments or can be fixed, inwhich case their front edge no longer pivots and their progressiveelastic profile is calculated so that the rear part adapts a suitablepropulsive inclination in response to vertical thrusts Ff and Fr.

The watercraft's degree of flotability is adjusted between 1 and 2, i.e.so that the volume of water displaced is from 1 to 2 times thewatercraft's laden weight, preferably between 1.2 and 1.5 depending onthe user's muscular strength and the desired degree of submersion.

FIG. 4a shows the submerged watercraft at the peak of its sinusoidalmovement where the blades 2 and 3 change position, the blade 2 pivotingin the direction of arrow F1 and blade 3 in the direction of arrow F2.This is the upper idle time of the sinusoidal movement.

FIG. 4b shows the sinking sinusoidal movement, where the blades 2 areagainst their upper and lower abutment respectively. Each blade producesa force perpendicular to its plane with a component in the direction ofpropulsion. The magnitude of this component increases with the anglethat the blade makes to the direction of propulsion.

FIG. 4c shows the perigee (low point) of the sinusoidal movement at themoment when the blade 2 pivots clockwise towards the lower abutmentwhile the rear blade has already pivoted against the upper abutment andexerts its thrust. It can thus be seen that the idle or dead points ofthe two blades do not coincide exactly so that the watercraftpractically constantly is thrusted forwards.

Lastly, FIG. 4d shows the watercraft in the upward phase of thesinusoidal movement where the two blades 2 and 3, working in phaseopposition, generate two propulsive forces which add together.

Of course, the sinusoidal movement of the watercraft is generated byalternately applying and removing the weight of the driver's body whereindicated by arrows Ff and Fr, which are directed alternately downwardsor upwards according to whether the driver applies his full weight ontoa point and pushes it down, or while alternately applying his weight onanother point the first point moves up under the effect of theArchimedes thrust and the lever effect due to the fact that theflotability is greater than 1 and preferably greater than 1.2.

The driver can hold onto a cord 11 secured to the front of thewatercraft. To steer, the driver displaces the points of application ofthe forces relative to the longitudinal axes A-A' by causing theseapplication points to pivot about the center of gravity in the clockwisedirection to turn left, and in the counter-clockwise direction to turnto the right, changing the direction of thrust of the blades 2 and 3relative to the longitudinal axis A-A'.

In practice, it is not necessary to displace the rear foot except whenthe front foot is angularly displaced by such a large amount that thedriver could no longer remain in equilibrium on the float.

The watercraft's turning radius depends on the angle of displacement ofthe foot or the feet. The more the front foot is eccentric to thelongitudinal axis, the more the blades 2 and 3 are inclined and causethe bow to chop, hence the turn is tighter. Moreover, by exercising astrong pressure on the front foot angularly offset to the longitudinalaxis A-A', the rear blade 3 is made to rise more or less out of thewater so that it no longer stabilizes the direction of the watercraft,which enables the watercraft to be practically rotated about itselfthrough a desired angle.

It should be noted that for steering, the position of the pivoting axis6 of the front blade is very important. The more this axis is forward inthe longitudinal direction, the more the blade is propulsive, but themore difficult it becomes to make a turn. To the contrary, the closerthis axis is to the center of gravity, the less propulsive is the blade,whereas making turns is easier.

In the vertical direction, the closer this axis is to the longitudinalaxis passing through the center of gravity, the more stable is thewatercraft, but it is then difficult to incline the blades laterally tomake turns. To the contrary, if the axis is lowered, stability decreasesbut making turns is easier.

The second embodiment of watercraft according to FIGS. 5 to 8 differsprincipally from the previous one due to the fact that the floatationelement is basically made up of the blades 12 and 13 themselves, theelement 14 connecting them being provided with transverse hinges 15 and16 for the two blades 12 and 13. As in the previous embodiment, the twoabutments 18a, 18b; 19a, 19b limit the amplitude of swing the blades 12and 13.

These abutments can be replaced by return biasing spring systems whoseforce is so calculated that the blades 12 and 13 adopt approximately thesame propulsive angle that they would have against the abutments duringthe vertical thrusts Ff and Fr.

Ballast is also provided in each blade for adjustment of thewatercraft's flotability according to the driver's weight.

Steering is achieved in the same way as before.

Propulsion is according to the same principle as for the firstembodiment, as can be appreciated from FIGS. 8 to 8d which require nofurther explanation.

Lastly, the embodiment of FIGS. 9, 10 and 11 includes a sort of floatingcarpet made up of four float elements 20, 21, 22, 23 hinged to oneanother with limited degrees of freedom relative to one another.

Because there are more than three hinged elements and therefore it isnot possible with two feet to control all of them, it is necessary toensure that the floating carpet cannot have adopt a blocked position inwhich propulsion is neutralized. In this case, to prevent such asituation from occurring, above and below the hinges spring blades 24are provided to tend to hold hinged-together pairs of elements relativeto one another. FIGS. 11a to 11d show the different phases aftersinusoidal movement and the resulting propulsive forces.

It must also be noted that the shape and the length of the float play apart in the watercraft's handling.

For each model, the best hydrodynamics is sought and as the volume ofthe watercraft is related to the driver's weight, each model will beavailable in several sizes.

For example, in the first embodiment, for a driver weighing 60/70 kg,the float can be about 1.8 m long, 50 cm wide mid-craft, and maximumthickness 28 cm for a volume of 100 liters. The front blade surface isabout 0.5 m². The rear blade surface about 0.25 m².

All of these figures can vary in wide proportions according to the aimsought: speed, stability, sporting movement.

Moreover, it is advantageous to provide a non-slip support for the feeton the float. For this purpose, a non-skid coating could be applied, andthe float fitted with binding straps.

Of course, the feet-supporting face of the float will be designed toallow angular displacement of the feet in order to steer and propel thewatercraft as explained above.

I claim:
 1. A muscle powered watercraft comprising:flotation structurehaving a floating member with feet supporting surfaces distributed abouta center of gravity of the watercraft, the volume of said floatingmember being selected to correspond to one to two times the total ladenweight of the watercraft, means for propelling said floating memberalong an axis of propulsion, said propelling means having at least twoblades which remain rigid under stresses they are subjected to, frontedges of the blades being hinged about respective fixed axes transverseto the watercraft's axis of propulsion, spaced from one another alongsaid axis of propulsion on either side of the watercraft's center ofgravity, each of the blades extending symmetrically from said axis ofpropulsion, the density of the blades being about that of water, andabutment means for limiting an angle of freedom of each blade about itshinging axis, and allowing each blade to convert a vertical force into apropulsion force, said feet supporting surfaces being distributed insuch a manner as to enable variation of the angle of propulsion of theblades relative to the watercraft's longitudinal axis, said watercraftbeing constructed and arranged such that a driver may impart to thewatercraft a sinusoidal movement in and out of the water by pitching thewatercraft and hence making the blades operate in opposition to oneanother against said abutments.
 2. A watercraft according to claim 1,further comprising means for varying a degree of floatation of thewatercraft.
 3. A watercraft according to claim 1, wherein the blades arehinged to a central element.
 4. A watercraft according to claim 2,wherein said varying means are constituted by a liquid phase arranged ina volume greater than that of said liquid phase and shaped to permit theflow thereof under the pitching effect communicated to said flotationstructure.
 5. A watercraft according to claim 2, wherein said varyingmeans are constituted by a solid phase formed of pellets arranged in avolume greater than that of said solid phase and shaped to permit theflow thereof under the pitching effect communicated to said flotationstructure.
 6. A watercraft according to claim 2, wherein said means areconstituted by a mixture of a liquid phase and a solid phase formed ofpellets, arranged in a volume greater than that of said liquid and solidphase and shaped to permit the flow thereof under the pitching effectcommitted to said floatation structure.
 7. The water craft according toclaim 1, wherein said flotation structure is selected to correspond to1.2 to 1.5 times the total laden weight of the watercraft.
 8. Thewatercraft according to claim 1, wherein the surface of the front bladeis larger than that of the rear blade.
 9. The watercraft according toclaim 1, wherein the pivoting axis of the front blade is positioned withrespect to the center of gravity so as to enhance turning of thewatercraft.